JP2543273Y2 - Tracking servo circuit of optical disk player - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking servo circuit for an optical disk player, and more particularly to a tracking servo circuit for improving settling immediately after a track jump in pause, still, manual search, multi-speed, and the like.

[0002]

2. Description of the Related Art In operations such as pause, still, manual search, and multi-speed in an optical disk player for reproducing a laser disk, a track jump for continuously jumping a laser spot to an adjacent track is performed.

FIG. 2 shows an example of such a conventional tracking servo circuit. As shown in the figure, the tracking error signal obtained from the optical pickup is input to the inverting input terminal of the operational amplifier 1 via the resistor R1, and is input to the tracking logic circuit 4. The non-inverting input terminal of the operational amplifier 1 is connected to the ground, and the output terminal is connected to the inverting input terminal via the impedance Z2.

The output terminal of the operational amplifier 1 is connected to the inverting input terminal of the operational amplifier 2 via a series circuit of a resistor R3 and a resistor R4. Further, a connection point between the resistors R3 and R4 is connected to the ground by a series circuit of the capacitor C1 and the analog switch S1. The constant current sources I1 and I2 are connected to one end of a resistor R5 via analog switches S2 and S3, respectively, and the other end of the resistor R5 is connected to an inverting input terminal of the operational amplifier 2.

The non-inverting input terminal of the operational amplifier 2 is connected to the ground, and the output terminal of the operational amplifier 2 is connected to the ground via a series circuit of the tracking coil 3 and the resistor R6. A connection point B between the tracking coil 3 and the resistor R6 is connected to the inverting input terminal of the operational amplifier 2 via a parallel circuit of the resistor R7 and the capacitor C2.

The tracking logic circuit 4 receives a jump signal in addition to the tracking error signal and turns on and off the analog switches S2 and S3.

In the above configuration, when the laser disk is being reproduced, the tracking logic circuit 4 opens the analog switches S2 and S3,
1, the tracking servo is turned on.

The tracking error signal is inverted and amplified according to the impedance ratio of the resistor R1 and the impedance Z2.
The current is supplied to the tracking coil 3 so as to be inverted and amplified at the resistance ratio and appear at the connection point B. Note that the capacitor C2 is provided for phase compensation. The tracking coil 3 is arranged in a magnetic field, and moves the objective lens integrated therewith so that the laser spot follows the signal pit row.

A slider servo circuit (not shown) drives the slider motor so as to reduce the DC component of the voltage at the connection point B, which is proportional to the tracking coil current. The slider on which the optical pickup is mounted is moved toward the outer periphery of the disk so that the line can be followed.

In a mode in which track jumps such as pause and still are repeated, the analog switch S1
Is closed to reduce the tracking servo gain, and FIG.
As shown in (a), a pulse-like jump signal is output at point A. When a jump signal is input, the tracking logic circuit 4 closes the analog switches S2 and S3 before and after, and supplies a reverse current to the tracking coil 3 before and after. The voltage at the point B proportional to the tracking coil current shown in FIG.

Due to such a pulse-like tracking coil current, a tracking servo with a reduced gain causes a laser spot to jump to an adjacent track. After the end of the jump, the analog switch S1 is opened, the tracking servo is applied, and the signal is reproduced. FIG.
(C) shows that the tracking error signal at point C fluctuates greatly during the jump period.

[0012]

In the conventional tracking servo circuit described above, after the jump is completed, the analog switch S1 is opened and the tracking servo is rapidly returned to the original high gain, so that the convergence is not performed smoothly and the settling time is long. There was a problem of becoming.

The constant current sources I1 and I2 are also used as brake current sources during a track search. During a track search, the tracking servo is repeatedly turned on and off while the optical pickup is being sent at a predetermined speed by the slider motor.

In the tracking off period, the objective lens performs a sinusoidal vibration centered on the neutral position supporting elasticity, and the constant current source I1 is used to converge the vibration of the objective lens.
Alternatively, a brake current using I2 as a signal source is supplied to the tracking coil 3. The end point of the tracking servo off period is detected by the decrease in the frequency of the tracking error signal, and the tracking servo is turned on.

As described above, since the constant current sources I1 and I2 are used as the brake current sources during the track search, the strengths of the constant current sources I1 and I2 are adjusted so that the tracking coil current during the jump becomes an optimum value. Could not be set, and the laser spot could not be smoothly jumped to an adjacent track.

The present invention has been made in view of the above points, and the purpose is to make the switching of the tracking servo gain after the end of the jump appropriate so that the smooth convergence is performed. An object of the present invention is to provide a tracking servo circuit for an optical disk player.

Another object of the present invention is to provide a tracking servo circuit of an optical disk player which can set a tracking coil current at the time of a jump to an optimum value independently of a brake current at the time of a track search. is there.

[0018]

According to the tracking servo circuit of the optical disk player of the present invention, each time a jump signal is received at the time of a track jump, pulse currents in opposite directions flow back and forth through the tracking coil and the period of the pulse current is controlled. In a tracking servo circuit of an optical disc player for lowering a servo gain, a pulse generating means for outputting a pulse for a certain period after receiving a pulse-like jump signal is provided, and a semiconductor switch for attenuating a tracking error signal by the pulse output; A semiconductor switch for shunting an input current serving as a signal source of the pulse current flowing through the tracking coil is made conductive.

[0019]

According to the tracking servo circuit of the present invention,
During a track jump, pulse currents in opposite directions flow through the tracking coil back and forth, during which time the servo gain is reduced and the laser spot jumps to an adjacent track. After stopping the pulse current, the servo gain increases. However, the tracking error signal input to the tracking servo circuit is attenuated by the semiconductor switch that is turned on by the pulse output of the pulse generation means, and the overall servo gain is reduced. Is kept lower than the normal tracking servo ON state.

After a predetermined period elapses after the pulse current of the tracking coil is stopped, the pulse output of the pulse generation means is stopped and the semiconductor switch for attenuating the tracking error signal is opened, and the servo gain of the entire tracking servo circuit is reduced to a normal value. It returns to the tracking servo ON state.
As described above, since the gain of the tracking servo is increased in two stages after the track jump, the laser spot smoothly converges on the signal pit train.

Further, the pulse output of the pulse generating means turns on a semiconductor switch for shunting an input current serving as a signal source of a pulse current to be passed to the tracking coil. The tracking coil current at the time of a jump can be set independently of the brake current at the time of a track search, and can be set to an optimum value for jumping to an adjacent track. In this way, the laser spot can be smoothly jumped to an adjacent track.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tracking servo circuit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment, and portions having the same functions as those shown in the conventional example are denoted by the same reference numerals.

In the circuit of the embodiment, the jump signal is input to a monostable multivibrator 5 which is a pulse generating means in addition to the tracking logic circuit 4. The resistance R1
Is connected to the ground by a series circuit of a resistor R8 and a digital transistor Q1, and the constant current input side of the resistor R5 is connected to the ground by a series circuit of a resistor R9 and a digital transistor Q2.

The output terminal of the monostable multivibrator 5 is connected to the base circuits of the digital transistors Q1 and Q2. The configuration and operation of the other parts are the same as those of the conventional circuit shown in FIG.

In the above configuration, in a mode in which track jumps such as pause and still are repeated, a jump signal is output from a microcomputer (not shown) as shown in FIG. When a jump signal is input, the tracking logic circuit 4 closes the analog switches S2 and S3 before and after during a period T shown in FIG. 3B, and supplies the tracking coil 3 with a current in the opposite direction before and after. During that time, the analog switch S1 is closed to lower the tracking servo gain, and the laser spot jumps to an adjacent track.

When the jump signal is input, the monostable multivibrator 5 outputs a high level for a predetermined period longer than the 2T period shown in FIG. 3B to make the digital transistors Q1 and Q2 conductive. As soon as the pulse current of the tracking coil stops, the analog switch S1 is opened and the servo gain increases.
Since 1 is conducting, the tracking error signal is attenuated, and the tracking servo to the target track is lightly applied.

Further, after a certain period of time, the digital transistor Q1 is shut off, the tracking servo gain is returned to a normal high state, and the target track is reliably tracked.

The currents of the constant current sources I1 and I2 serving as the pulse current sources of the tracking coil are divided by the resistor R9 and the digital transistor Q2. At the time of track search, the digital transistor Q2 is in a cutoff state,
By setting the resistance values of the resistors R5 and R7, the brake current is set to an optimum value. Then, by setting the resistance value of the resistor R9, the tracking coil pulse current at the time of the track jump is set to the optimum value.

[0029]

According to the tracking servo circuit of the present invention, the tracking coil pulse current at the time of a track jump is set to an optimum value independently of the brake current at the time of a track search. After the jump is completed, the gain of the tracking servo is increased stepwise, so that the convergence of the servo is improved and the settling time is shortened.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a tracking servo circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a conventional tracking servo circuit.

FIG. 3 is a waveform diagram of a signal indicating an operation of the tracking servo circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Operational amplifier 2 Operational amplifier 3 Tracking coil 4 Tracking logic circuit 5 Monostable multivibrator Q1 Digital transistor Q2 Digital transistor

Claims (1)

(57) [Scope of request for utility model registration] In a tracking servo circuit of an optical disc player, a pulse current in a direction opposite to each other is supplied to a tracking coil before and after each time a jump signal is received during a track jump and a servo gain is reduced during the pulse current. A pulse generating means for outputting a pulse for a certain period of time after receiving the jump signal, a semiconductor switch for attenuating a tracking error signal by the pulse output, and an input current serving as a signal source of the pulse current flowing to a tracking coil. A tracking servo circuit of an optical disk player configured to conduct a shunted semiconductor switch.